It is known in the art of roofing, to manufacture roof covering materials of the shingle or tile type by applying granules to a bituminous coated substrate, for use as roofing shingles, or as a rolled roofing product.
Typically, the substrate is a fiberglass or natural fiber mat, that is coated on its opposite sides with a bituminous material, generally asphalt, usually by immersing the mat in the bituminous material. Then, it is known to apply granules of a given size, to the surface of the bituminous coated substrate that is to be weather-exposed in the installed condition on a roof Usually smaller particles, such as sand, mica or talc are applied to the opposite side of the bituminous coated mat, to prevent adjacent shingles in a stack of shingles that are being shipped to the site of application, from sticking to each other, and to make the resultant shingles or other roof covering material more easily handleable. Often the shingle material is then cut to form various shapes, such as three-four tab shingles, rolled roofing, or the like. Various aesthetic effects may be obtained by using different cuts to form slots or spaces between adjacent tabs, and/or by using granules of different colors or different color combinations, to achieve different aesthetic or ornamental effects.
Representative known techniques include those disclosed in U.S. Pat. Nos. 6,038,826; 6,092,345; 6,355,132; 4,352,837; 5,181,361; 5,375,491 and many others.
The granules that are applied to the weather-exposed surfaces of the shingles or other roof covering material are generally, in part, embedded in the bituminous material, and the portions of the granules that are not thus embedded protect the surface of the bituminous material from absorbing excess heat from sunlight. Frequently the granules also deflect ultraviolet light, and the granules can also be treated with antifungal solutions, solar reflective treatments, color retention solutions, flame retardants, and many other substances.
Because the granules are applied to the weather-exposed surfaces of the roofing materials, the granules can become damaged by roofing workers walking on the roof, which may crush or dislodge the granules or otherwise damage the granules or weaken their adhesion to the roofing materials. Additionally, granules can become damaged or dislodged by impact from being struck by objects such as hail, ice, snowballs, tree branches falling on the roofing materials and likewise dislodging or damaging the granules, or by any other means by which the granules of roofing products may be subject to abuse.